Add an optional vendor_cause string to
RIL_REQUEST_LAST_CALL_FAIL_CAUSE's response.
This vendor cause string will be passed to Telecom's DisconnectCause,
which could help us figure out why we are seeing so many ERROR_UNSPECIFIED.
bug:17701976

Original partner change:
https://partner-android-review.googlesource.com/#/c/215710/

Change-Id: I0c54733a03b2fe2bd48b3d3b21efc5e3ebd9ef66
3 files changed
tree: 8337d7208976aecc2517dba4260abe3a491501c1
  1. include/
  2. libril/
  3. librilutils/
  4. reference-ril/
  5. rild/
  6. CleanSpec.mk